where $f(\epsilon_{eff}^p)$ is a user defined CURVE.
Ductile failure is modeled with the Cockcroft-Latham failure criterion.
A rebar element will be eroded once a damage parameter, $D$, has evolved from 0 to 1.
The damage is defined as:

where $\sigma$ is the tensile stress in the rebar. Note that damage only grows in tension (i.e. if $\sigma > 0$).
$\tau_{max}$ is the maximum shear resistance between rebars and concrete. At shear stresses above $\tau_{max}$ the
rebars begin to slide inside the concrete. In the current implementation, the shear resistance is maintained at $\tau_{max}$ even after
initiation of sliding.